A conventional solar heat power generation device generates power using solar heat. This solar heat power generation device typically generates power by collecting sunlight using collecting means, heating a heat medium in a solar heat collection tube using the collected sunlight, and using the thermal energy of the heated heat medium in a generator. The solar heat collection tube has a duplex tube structure formed from a metal inner tube through which the heat medium can flow, and a glass outer tube. Further, in order to suppress heat loss caused by heat radiation, a vacuum is typically maintained between the inner tube and the outer tube, and in order to absorb a thermal expansion coefficient difference between the inner tube and the outer tube, the two tubes are typically connected via thermal expansion difference absorbing means such as a bellows.
The glass tube (a glass tube used for a solar heat collection tube) serving as the outer tube of the solar heat collection tube having this structure requires a high degree of optical transparency in order to transmit the sunlight efficiently. Typically, when sunlight enters the glass tube, approximately 4% of the sunlight (100%) reaching the glass tube is reflected by each of an outer surface and an inner surface of the glass tube, and therefore approximately 92% of the sunlight passes through the glass tube of the solar heat collection tube. Hence, a method of forming an anti-reflection film on at least one of the outer surface and the inner surface of the glass tube used for the solar heat collection tube in order to reduce sunlight reflection by the glass tube used for the solar heat collection tube has been proposed (Patent Document 1, for example).
Patent Document 1: Japanese Patent Application Laid-Open No. 2004-239603